Perhaps by the time he started feeling this way, it was too late to relicense? Megacorps would just fork from a pre-GPL release and carry on.

that's my understansing as well.

I'm not judging the author here, but on one hand I understand the frustration, on the other hand the package probably owes its popularity in part to its very permissive license.

Anyway, a fork maintained by the companies that use the package would still be a better outcome than keep working for them for free (or remove the package entirely).

Would GPL help though? It's a library used by tests, not part of the end product distributed to users.

I don't know in this case but in general a GPL fork must stay GPL and, AFAIUI, importing a GPL package in your code it's similar to linking to it, so if the code that uses your GPL package is published (on GH for example) that could be considered redistribution. Not sure about the legalities but it could create enough friction to keep companies not willing to contribute away.

I guess I'm thinking more in terms of faker, which I believe was a library for creating test data. Makes me wonder if licenses matter much for tools that are never intended to be included in the final distribution.

Internal changes aren't going to be detectable, so it feels like the best you can hope for is that they don't want the maintenance burden of a patch set on top of your project. At that point it's not much different than MIT.

That said, AGPL would scare off most companies :p

Yes, especially GPLv3. Still open source, and companies avoid it.